The Bitx40 Project as built by N6QW

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Somewhere in the time period 2003/2004 an ingenious ham from India, Ashar Farhan VU2ESE, came up with a revolutionary concept. The idea was a simple design for a low cost easy to build SSB transceiver! His transceiver design was aimed at many of the hams in his native India that wanted to share the joy of talking across the ionosphere; but unfortunately were on a limited budget. To make the project cost efficient, a bilateral design concept was employed were many of the same circuits were used both on transmit and receive. The part count was very low and for the most part employed the common 2N3904 transistor (about one dozen). Sensing the lack of parts such as ferrite core transformers his suggested alternative for coil forms were nylon washers.* For an output device the IRF510 was pressed into service which yielded about 5 watts on 20 Meters. The project was a huge success and forward to today, thousands have been built world wide. I almost failed to mention that most of his design was done while on a long airplane flight from India to the UK. Common folklore has it that he used the calculator in his smart phone and most of the design was on the backs of cocktail napkins. VU2ESE's original Bitx20 project can be found here.

Shortly after going public with his project I built one in the Spring of 2004. You can see my rig in the photo below. My call at that time was W6JFR.

[* The design I used (his original) specified the nylon washers which I converted to ferrite core transformers and here is the conversion .]

The radio worked pretty well and my contribution was to add a VFO stabilizer and LCD display. Pretty "uptown" for 2004! There is a Bitx20 users group on Yahoo Groups and if you are reading this and are not already a member this is a must join group .

Fast forward to today and now Farhan has taken the project one step further and is offering a complete built Bitx40 with all the hardware for the amazing sum of $45 shipped from India. [That was the offering in Novemeber of 2016.] You can find the detail of this offering here . The rig is fully built and tested and the only effort on the part of the buyer is to fit the radio to a suitable enclosure, install the controls and wire the controls to the single board rig. The board is fitted with header pins and wire bundles included with the kit have the mating connector that plug into the board. The builder is left with the task of soldering the other ends of the cable bundles to the controls and installing it in an enclosure of their choice.

The most recent offering of the kit ( January 2017) now includes the Digital VFO Option complete with an LCD display and Si5351 Phase Locked Loop Clock Generator. The price for the Bitx40 board and "Digi" VFO is $59. [Note: I can't buy the parts for $14 --so a bargain indeed!]

The Bitx40 is fully operational out of the box and even includes the microphone element. Frequency control is by means of a varactor tuned VFO. But the intent of the board is for experimentation and one area that is available to the user is to replace the varactor VFO with a DDS (Direct Digital Synthesizer) or PLL (Phase Locked Loop Clock Generator) so that there is no drift and the readout is highly accurate. It is strongly recommended that the rig be initially built "as supplied". It is whole order of magnitude of difficulty to jump right into a DDS or PLL, even for an experienced builder. Thus get it working first as supplied by Farhan, then you have a benchmark of performance.

I have just started working on my Bitx40 and am at the point of connecting the wires to the controls. I will be using an Ardunio Pro-Mini to drive an AD9850 DDS to supply the LO (Local Oscillator) signals. We are probably several days before we are ready for an on the air test hopefully before Christmas 2016.

How to start the build of the Bitx40?

All of us suffer from impatience! The arrival of the Bitx40 typically takes about three weeks via India Post. The rigs get shipped very quickly but it still takes three weeks to get it in your hot hands. The first thing you DON'T want to do is haywire it together in about 10 minutes only to find out you have blown up your new rig.

I will present to you an ordered method for completing your rig and getting it on the air while trying to avoid the problems that haste often brings. With apologies to builders who have been around the horn my approach assumes that the builder is just starting out building a first time project. You are never too old to learn something. I have developed my approach into phases and as this website develops there will also be you tube videos with links that will support the phases.


he Arduino/AD9850
Phase 1: Getting Organized ~ The Noodling Effect!
Phase 2: Initial Layout of the Rig ~ Thinking in the Box
Phase 3: Mechanical operations ~ Punching/Drilling/Filing
Phase 4: Fit Check and initial wiring
Phase 5: Initial testing without power applied
Phase 6: Power on Testing
Phase 7: Adding the Arduino / AD9850 & OLED + Si5351
Phase 8: Hacking the Bitx40

Post Script: My Bitx40 has been on the air and in just one day made four contacts with stations in Arizona and Nevada. Typically the distance was in the 200 to 300 mile range. The signal reports were telling in that the signal quality and "punchy audio" were considered to be quite good --but you know the OF's (Old Farts) on 40 Meters, they complain if your signal is not 40/S9. There is even a video of the first contact which can be seen here.